WIND

The horizon, besides being divided into 360 degrees, like all other circles, is by mariners supposed to be divided into four quadrants, called the north-east, north-west, south-east, and south-west quarters. Each of these quarters they divide into eight equal parts, called points, and each point into four equal parts, called quarter-points. So that the horizon is divided into 32 points, which are called rhumbs or winds; to each wind is assigned a name, which shews from what point of the horizon the wind blows. The points of north, south, east, and west, are called cardinal points; and are at the distance of 90 degrees, or eight points from one another.

Winds are either constant or variable, general or particular. Constant winds are such as blow the same way, at least for one or more days; and variable winds are such as frequently shift within a day. A general or reigning wind is that which blows the same way, over a large tract of the earth, almost the whole year. A particular wind is what blows, in any place, sometimes one way, and sometimes another, indifferently. If the wind blows gently, it is called a breeze; if it blows harder, it is called a gale, or a stiff gale; and if it blows with violence, it is called a storm or hard gale. The swiftness of the wind in a great storm is not more than 50 or 60 miles in an hour; and a common brisk gale is about 15 miles an hour (Robertson's Navigation.).

The following observations on the wind have been made by skilful seamen; and particularly the great Dr. Halley.

1st. Between the limits of 60 degrees, namely, from 30� of north latitude to 300 of south latitude, there is a constant call wind throughout the year, blowing on the Atlantic and Pacific oceans; and this is called the trade-wind.

For as the sun, in moving from east to west, heats the air more immediately under him, and thereby expands it; the air to the eastward is constantly rushing towards the west to restore the equilibrium, or natural state of the atmosphere; and this occasions a perpetual east wind in those limits.

2d. The trade-winds near their northern limits blow between the north and east, and near the southern limits they blow between the south and east.

For as the air is expanded by the heat of the sun near the equator; therefore the air from the northward and southward will both tend towards the equator to restore the equilibrium. Now these motions from the north and south, joined with the foregoing easterly motion, will produce the motions observed near the laid limits between the north and east, and between the south and west.

3d. These general motions of the wind are disturbed on the continents, and near their coasts.

For the nature of the soil may either cause the air to be heated or cooled; and hence will arise motions that may be contrary to the foregoing general one.

4th. In some parts of the Indian ocean there are periodical winds, which are called Monsoons; that is, such as blow half the year one way, and the other half-year the contrary way.

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